How to plot 2D Linear Inequality?

How to plot cond1 and cond2 with the cost in one figure?

 [x1,x2]=meshgrid(0:.1:10,0:.1:10);
 cond1=x1-x2<=-2;
 cond2=-0.3*x1-x2<=-8;
 cost=0.4*x1.^2-5*x1+x2.^2-6*x2+50;
  figure (1)
 contour(x1,x2,cost,10,'linewidth',2)
 xlabel('x_{1}');
 ylabel('x_{2}');
 hold on
 ...

[Omar B.]

How to get this pic?

Answer 1

[KSSV]

 [x1,x2]=meshgrid(0:.1:10,0:.1:10);
 cond1=x1-x2<=-2;
 cond2=-0.3*x1-x2<=-8;
 cost=0.4*x1.^2-5*x1+x2.^2-6*x2+50;
 figure (1)
 contour(x1,x2,cost,10,'linewidth',2)
 hold on
 contour(x1,x2,cond1,'color','k','linewidth',2)
 contour(x1,x2,cond2,'color','r','linewidth',2)
 xlabel('x_{1}');
 ylabel('x_{2}');
 hold on

[Omar B.]

Thank you. Why don't they look linear? can we use plot?

[KSSV]

clc; clear all ;

 [x1,x2]=meshgrid(0:.1:10,0:.1:10);
 cond1=x1-x2<=-2;
 cond2=-0.3*x1-x2<=-8;
 cost=0.4*x1.^2-5*x1+x2.^2-6*x2+50;
 %% Get cond1 and cond2 
c1 = contour(x1,x2,cond1,[1 1],'color','k') ; 

idx = c1(2,:)>max(x2(:)) ; 
c1(:,idx) = [] ; 
p = polyfit(c1(1,:),c1(2,:),1) ; 
c1(2,:) = polyval(p,c1(1,:)) ; 
%
c2 = contour(x1,x2,cond2,[1 1],'color','k') ; 

idx = c2(2,:)>max(x2(:)) ; 
c2(:,idx) = [] ; 
p = polyfit(c2(1,:),c2(2,:),1) ; 
c2(2,:) = polyval(p,c2(1,:)) ; 

 
 figure (1)
 contour(x1,x2,cost,10,'linewidth',2)
 hold on
 plot(c1(1,:),c1(2,:),'k','Linewidth',2)
 plot(c2(1,:),c2(2,:),'k','LineWidth',2)
 xlabel('x_{1}');
 ylabel('x_{2}');

[Omar B.]

Thank you so much.

[Omar B.]

could you please explain what do you mean by c1(2,:) and c1(1,:)?

[KSSV]

Coordinates of contour lines are obtained. Those are c1, c2. These coordinates are row arrays. c1(1,:) means first row which is x -coordinate and c1(2,:) is second row which is y-coordinate.

[Omar B.]

I got it. Thank you so much.